(1) Field of the Invention
This invention relates to a method of determining an operating path of a tool in relation to a surface of a workpiece, wherein a plurality of points of contact between a tool and the workpiece surface are determined and information in the form of digitised co-ordinate axis values relating to each determined point of contact is stored in a computer memory device, from which a set of co-ordinate axis values an operating path for the tool can be derived.
(2) Summary of the Prior Art
In U.S. Pat. No. 4,136,306 is disclosed a sewing machine for digitising a predetermined pattern and thereafter stitching the predetermined pattern on a workpiece, in the use of which machine a model pattern is moved under operator control along co-ordinate x and y axes successively to bring so-called "stitch points" into an appropriate relationship with an operating tool, the stitch points thus constituting points of contact between the tool and the workpiece surface. In operation, in such machine, furthermore, the operator uses a so-called "joy stick switch" which generates signals and supplies them to a computer which serves to convert the signals to drive signals for motors by which the x and y axis movement is effected. When each stitch point is properly aligned with the tool, furthermore, the co-ordinate axis values can be digitised and stored in the computer memory, and from the set of co-ordinate axis values thus obtained the operating path of the tool in relation to the workpiece surface can be derived.
Whereas the aforementioned method of digitising a pre-determined pattern has been found to be satisfactory where a prepared model pattern is supplied, the method described does not in any way assist in the determination of the location of the successive points of contact, still less the spacing between them. The method is therefore limited in its application in that a prepared model pattern is required for each style of workpiece to be operated upon. In addition, while said method has proved satisfactory for use with two-dimensional workpieces, the preparation of a model pattern for a three-dimensional surface, e.g. a shoe bottom, would be time-consuming and generally lead to greater difficulties than envisaged with a two-dimensional surface.
It is thus the object of the present invention to provide a method for determining each point of contact between a tool and a workpiece surface and for controlling the spacing between adjacent points, specifically for use with a method of determining an operating path of a tool in relation to such surface.